the school from - Clamp School Detectives it's basically a small city. here is the wikipedia info

The Clamp School is the brainchild of the Imonoyama zaibatsu. It is placed in a sprawling estate as big as a small city. Each of the five corners houses one of the five school divisions, which range from kindergarten through college, even graduate school. It also is a self-contained campus in Tokyo, it having its own city, complete with banks, shopping arcades, public utilities, as well as its own mass rapid transit system. The Clamp School's mission is to cater to all talented students, rich or poor.